The present invention relates to the field of voice and data communications, and in particular, a method and apparatus for coupling a voiceband modem circuit to a common phoneline connector for use in a home network communications system.
Referring to FIGS. 1a-1e, an evolution of home based communications systems is depicted.
In FIG. 1a, plain old telephone service (POTS) wiring 102, generally unshielded twisted pair (UTP) wiring, at customer premises 104 couples POTS telephones 106 through subscriber loop 108 to a telephone company central office, which, in turn, is connected to the public switched telephone network (PSTN). Customer premises 104 is a telephone subscriber site that has arranged (generally for a monthly telephone service fee or for a per call minute fee) with a local provider (such as a local telephone company) for a connection to the central office. The central telephone office (also called a local exchange) provides local switching and non-local switching via the PSTN.
In FIG. 1b, computer 110 through conventional voice modem 112 can also be coupled to POTS wiring 102 to allow the transmission of signals from computer 110 to be transmitted onto the telephone network. Voice modem 112 will be described in more detail below.
In FIG. 1c, there is depicted a conventional local area network (LAN) 114 (such as an ethernet network using coaxial cable) installed at customer premises 104 in addition to any POTS wiring 102 that may be in place to connect, for example, computer 110 with computer 110a. 
In FIG. 1d, computers 110 and 110a, rather than being connected via LAN 114 as seen in FIG. 1c, connects and utilizes POTS wiring 102 as a LAN transmission medium in accordance with the Home Phoneline Network Alliance (HPNA) specifications for the LAN computer interconnection over existing telephone lines within the local environment.
In FIG. 1e, computer 110, while implementing an HPNA LAN via POTS wiring 102, can also implement broadband digital data services through digital subscriber line (xDSL) modem 116, including one which supports asymmetrical digital subscriber line (ADSL) protocol, coupled to POTS wiring 102.
While broadband data services using DSL, or similarly cable modem or fixed wireless transceivers, are now being regularly deployed in home environments, there is still a need for basic connectivity using legacy voiceband data modems. Moreover, in the case of DSL and particularly ADSL, the broadband service may use the same physical metallic pair over which the voiceband modem signals travel to the PSTN central office, though at higher frequencies. In many cases, there may be no splitter (low-pass filter) between the in-premise wiring and the local loop.
Therefore, a need exists for a method and apparatus for attenuating high-frequency interfering signals, such as splitterless ADSL or phoneline network signals, at the front-end of a voiceband modem. The present invention provides a solution to this problem and will enable low-cost voiceband modems which use line-powered DAAs to be able to effectively connect to the PSTN.